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MathGroup Archive 2007

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Re: Dot or Inner ... but not quite

  • To: mathgroup at smc.vnet.net
  • Subject: [mg79655] Re: [mg79622] Dot or Inner ... but not quite
  • From: Carl Woll <carlw at wolfram.com>
  • Date: Wed, 1 Aug 2007 05:01:44 -0400 (EDT)
  • References: <200707311013.GAA21053@smc.vnet.net>

Diamond, Mark wrote:

>I have two equi-length lists, the first of number, the second of 
>(equi-length) lists of numbers , such as
>
>l1={1,4,3};
>l2={{1,7},{1,9},{5,2}};
>
>I want to produce 1*{1,7}+4*{1,9}+3*{5,2}
>
>It looks so close to Inner that I thought I could use it in some form, but I 
>have ended up using
>
>(#[[1]]*#[[2]])& /@ Transpose[{l1,l2}]
>
>Is there a better way using one of the builtin functions with which I am 
>unfamiliar?
>
>Cheers,
>
>Mark Diamond 
>
>
>  
>
How about

In[89]:= Total[l1 l2]

Out[89]= {20,49}

Carl Woll
Wolfram Research


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